# IV calculation

Published

hi everyone! school starts tomorrow! i am excited/nervous:D:uhoh3:. As I was going through some math problems,I encountered this one problem and I am a bit confused! Here is the question:

The physician has ordered a bolus of 400 mL over 4 hours .After 2 hours, 300 mL remain in the bag. Hospital policy allows a 25% increase in the IV rate to compensate for the slow infusion.

a. what is the new rate?

My instructor said to solve for the mL/hr : 400mL/4 hrs= 100mL/hr and then she did this: 100mL * 1.25= 125 mL/hr. Now my question is: why 1.25?does it have something to do with percent? Is that the reason why we she put 1 in front of. 25?? I thought at first that to solve for the new rate,I should do this: 300mL/ 2hrs??

b. how long will the balance of the infusion take?

125 mL/hr = 300mL/x

x= 2.4 hrs.

HELP!

1 Article; 102 Posts

Specializes in ICU. Has 5 years experience.

Well start with the original rate of 100ml and hour and know that you can only increase by 25% or 0.25, so you multiply the rate times 1.25 to receive 125% of the original rate. Now the orginal rate was easy, 100ml an hour but it may have been something weird like 67 ml per hour, at which you would multily it by 1.25 and receive the new adjusted rate of 84ml per hour ( rounded).

ps You were right partial about dividing the 300ml/2hours to find out how fast to run the rate to achieve the original order, but your forgetting you can not increase the rate more than 25% which that problem would have done. The way you were originally doing it would have increased the rate by 50%!

49 Posts

hi!

thanks for your response! so im assuming that if I see a 25 % or whatever the hospital policy is, I should consider that and solve for the original rate then multiply by (whatever % is given). is that right?

1 Article; 102 Posts

Specializes in ICU. Has 5 years experience.

Yes. Now the adjusted rate may be less than 25% or it may be going too fast ( unlikely but possible) in which case you would decrease the rate. For instance in the case you mentioned due to what ever complication ( bent elbow or something) the rate needed to be increased by 50% to reach the original order, but this would be in violation of hospital policy in which you could only increase the rate by 25%. In the above case, you would probably need to contact the MD to let them know that due to complications the medication had to be given over 5 hours (or what ever it works out to be)

49 Posts

a few other questions!

1. Order: Heparin 7000 units SQ Q6H

Available: 10,000 units /mL

how many mL/dose?

is this right? i solved it like this:

mL/dose= 1mL/10,000 units x 7000 units/1dose= 0.7 mL/dose ( i was thinking of i should even consider writing 6hrs under 7000 units ,but i didn't because 1 dose means pt gets 7500 units.right?

2. Order: D5W 1150mL IV q6h. Tubing calibrated at 10 gtts/mL. Calculate gtts/min.

i did it like this:

gtts/min: 10 gtts/mL x 1150 mL/6hrs x 1hr/60mins= 31. 9 or 32 gtts/min (so for this one you would really have to write the 6hs under 1150mL?

i dont know if i am just overthinking or what!

1,049 Posts

Specializes in Vascular Access. Has 32 years experience.
a few other questions!

1. Order: Heparin 7000 units SQ Q6H

Available: 10,000 units /mL

how many mL/dose?

is this right? i solved it like this:

mL/dose= 1mL/10,000 units x 7000 units/1dose= 0.7 mL/dose ( i was thinking of i should even consider writing 6hrs under 7000 units ,but i didn't because 1 dose means pt gets 7500 units.right?

2. Order: D5W 1150mL IV q6h. Tubing calibrated at 10 gtts/mL. Calculate gtts/min.

i did it like this:

gtts/min: 10 gtts/mL x 1150 mL/6hrs x 1hr/60mins= 31. 9 or 32 gtts/min (so for this one you would really have to write the 6hs under 1150mL?

i dont know if i am just overthinking or what!

Yes, You're overthinking this... The answer to number one is 0.7mls every 6 hours

and the answer to number two is also correct, 32 gtts/min .... Period.

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